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Cranelift: Correctly wrap shifts in constant propagation (#5695)

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Fixes #5690
Fixes #5696

Co-authored-by: Jamey Sharp <jsharp@fastly.com>
This commit is contained in:
Nick Fitzgerald
2023-02-02 16:12:57 -08:00
committed by GitHub
parent fd67ccf9cd
commit 72c8513411
10 changed files with 176 additions and 35 deletions
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16
cranelift/codegen/src/opts/algebraic.isle
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@@ -191,15 +191,15 @@
;; `(x >> k) << k` is the same as masking off the bottom `k` bits (regardless if
;; this is a signed or unsigned shift right).
(rule (simplify (ishl (fits_in_64 ty)
(ushr ty x (iconst _ (u64_from_imm64 k)))
(iconst _ (u64_from_imm64 k))))
(let ((mask u64 (u64_shl 0xFFFFFFFFFFFFFFFF k)))
(band ty x (iconst ty (imm64_masked ty mask)))))
(ushr ty x (iconst _ k))
(iconst _ k)))
(let ((mask Imm64 (imm64_shl ty (imm64 0xFFFF_FFFF_FFFF_FFFF) k)))
(band ty x (iconst ty mask))))
(rule (simplify (ishl (fits_in_64 ty)
(sshr ty x (iconst _ (u64_from_imm64 k)))
(iconst _ (u64_from_imm64 k))))
(let ((mask u64 (u64_shl 0xFFFFFFFFFFFFFFFF k)))
(band ty x (iconst ty (imm64_masked ty mask)))))
(sshr ty x (iconst _ k))
(iconst _ k)))
(let ((mask Imm64 (imm64_shl ty (imm64 0xFFFF_FFFF_FFFF_FFFF) k)))
(band ty x (iconst ty mask))))
;; Rematerialize ALU-op-with-imm and iconsts in each block where they're
;; used. This is neutral (add-with-imm) or positive (iconst) for